Behgek



F. VON WURSTEMBERGER.

METHOD AND DEVICE FOR THE PREVENTION OF SELECTIVE CORROSION 0F METALLIC PARTS.

APPLICATION FILEI) IAN. I4, 1922.

1,435,268. I 4 Patented Nov. 14, 1922.

Patented Nov. 14, 1922.

entree stares Ltttfitt PATET @FWQE.

FRANZ VON WURSTEMJBERGER, OF ZURICH, SWITZERLAND.

METHOD AND DEVICE FOR THE PREVENTION SELECTIVE CORROSION F METALLIC PARTS.

Application filed January 14, 1922. Serial No. 529,170.

To all whom it may concern Be it known that I, FRANZ voN' Wons'rmn BERGER, a citizen of the Re ublic of Switzerland, residing at Zurich, witzerland, have 1 5 invented a certain new and useful Improvement in Methods and Devices for the Prevention of Selective Corrosion of Metallic Parts, of which the following is a specification, reference being had therein to the accompanying drawing.

Experiments have shown that "metallic parts'in machinery and apparatus and the like made of copper or copper containing alloys which are in contact with water containing ions, especially sea water, are particularly subjected to destruction by selective corrosion when said water is stagnant as in this case various electrolytical conditions appear on various parts of the metal surface, which conditions may be the cause of the formation of local galvanic-action. The effect of this action is visible particularly in the form of channel shaped corrosions in the metallic parts around spots at which solid materials of any kind are in contact with the metal surface. In this manner superposed particles of materials that are electrically indifi'erent as such, for instance glass, may become the cause of selective corrosion. It is also to be noted that the products of decomposition formed by such local corrosions and particularly the alkalinity arising thereby, increase further the corrosive qualities of the Water.

As dangerous working conditions are to be considered for instance, with regard to condensers of steam power stations when out of operation during the night and with regard to steam ships for the periods during which they are in the harbours.

The object of the present invention is a method for the prevention of selective corrosions of metallic parts in machinery, apparatus and the like made of copper or copper containing alloys and arising from the corrosive action of water containing ions, particularly of sea water, and an installa tion for carrying out said method. According to the invention the liquid is constantly 350 kept in motion, as long as the metallic parts are in contact with the li uid, so that nowhere stagnant water wil act upon the metallic parts.

In the accompanying drawing several convention are diagrammatically illustrated. In

this drawing:

Fig. 1 shows a surface condensing plant provided with a main pump and an auxiliary pump adapted to force water through the condenser;

Fig. 2 illustrates a surface condensing plant having a single pump for forcing water, which pump can be worked under difierent delivery conditions;

Figs. 3 and 4 show further'surface condensing plants having a single pump, to the delivery branch of the latter a water reservoir or a water main respectively is connected.

The useful effect of circulation of liquids for preventing corrosion was first discovered in numerous practical laboratory tests where it was found that in stagnant salt Water local corrosion occurs at any spot of the surface of copper or. copper alloy, Where the latter is in contact with any neutral body, such as glass, porcelain or ebonite. At such points the red, protoxyde of copper is formed and the corrosion may go to a considerable depth into the metal. If, however, the liquid is maintained in motion, no such corrosion takes place, but a homogeneous layer of oxychloride is formed.

The explanation of this phenomenon has been found in the chemical reaction which may occur.

First, a certain formation of cuprous ions takes place, that is to say a production of cuprous chloride:

1 ou+Nao1+HoH=cuc1+Naon+H but this reaction soon ceases because of the polarizing effect of the produced CuCl. Thus an equilibrium is established. However, a second reaction takes place:

(2) CuCl+NaOH=CuOH+NaGl thus transforming the CuCl into the yellow or red hydroxyde, CuOH. The CuOH being quite insoluble, it posesses quite a small concentration of cuprous ions, at any rate a smaller one than that of CuCl. Areas of copper surface covered with CuOH situated besides areas covered with CuCl comport themselves electrolytically like zinc in contact with copper and a new electrolysis starts.

' tion of NaOH according to reaction (1) and upon the quantity of water into which the produced NaOH spreads by diffusion. In stagnant water, therefore, areas of quite different alkalinity will be formed. Areas of a copper surface. where the free diffusion is hindered by bodies in contact, will soon be enveloped with an electrolyte much more alkaline than neighboring areas and thus be endangered by corrosion.

If, however, the water is maintained in circulation a constant levelling of electrochemical conditions, primarily of the alkalinity, takes place over the whole surface of the metallic parts and in this way the causes of selective corrosion are pre vented.

Numerous researches by me have shown that corrosion is chiefly an electro-chemical problem. The areas acting as electrodes are, however, not areas of different potential caused by unhomogenous alloy, but by unhomogenous deposition of surface layers of the copper salts formed.

Referring to the constructional example illustrated in Fig. 1, 1 denotes the surface condenser which contains as heat exchanging organ a nest of tubes 2. A. pump 3' forces for instance sea water from a supply ditch 4 through the condenser into a discharge ditch 5. If now the plant is not working the stagnation of the salt containing water would endanger more or less the condenser tubes 2 and the bronze parts in the interior of the pump 3. To remedy this danger an auxiliary pump 6 is provided which continuously, and therefore also during the stoppage of the main pump 3, forces water through the main pump 3 into the condenser 1. The output of the auxiliary pump is such that throughout the branches of the tubes 2 a small circulation of water is ensured. Any flowing back of the water to the ditch 4: is prevented by a suitable non-return Valve 7.

Instead of providiiTg a separate auxiliary pump the main pump 3 may be designed so as to be able to deliver a much reduced quantity when the water delivered is not utilized for working the plant but only for preventing a stagnation of the liquid in parts of the plant. An installaton of the type described is shown in Fig. 2, in which provision is made for the speed of the pump 3 and thereby for the quantity delivered and the delivery head to be altered by means of a belt drive 8 and step pulleys. Instead of anauxiliary pump a reservoir 9 (Fig. 3) may be provided from which water flows through the condenser 1 during the stopping of the plant, or the condenser may be connected up to water supply mains 10 (Fig. 4) in such a manner that upon opening the connection a stagnation of liquid in the plant is prevented.

I claim:

1. A method for the prevention of selective corrosion of metallic parts made of copper and copper containing alloys in machinery, apparatus and the like, comprising keeping the liquid in contact with metallic part-s continuously in motion as long as said contact occurs and preventing thus the corrosive effects caused by the action of stagnant water contaning ions upon said metallic parts.

2. In an installation of' the type described, an apparatus having metallic parts made of copper and copper containing alloys, in which water containing ions is in contact with said parts, means to cause a continuous motion of said water for preventing the corrosive effects caused by the action of stagnant water upon said metallic parts.

3. In an installation of the type described, an'apparatus having metallic parts made of copper and copper containing alloys, in which water containing ions is in contact with said parts, a pump to cause a continuous motion of said water for preventing the corrosive effects caused by the action of the stagnant water upon said metallic parts.

In testimony whereof I afiix my signature.

FRANZ VON WURS'IEMBERGER. 

